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How Auto Current Mode works
The Cellpro 4s Charger’s Auto Current Mode precisely monitors individual cell fuel levels
(cell voltages) in a pack. If the charger determines it is charging too fast, it slows down.
Likewise, if it is charging too slow, it speeds up. The charger adjusts charge current at one
minute intervals throughout the charge cycle.
When charging starts, it takes a short time for the charger to determine the correct parameters,
so it may “hunt” for up to five minutes before it settles on the optimum current. This is nor-
mal, and doesn’t harm the pack. The longer the charge, the more accurate the calculation.
The plot below shows how Auto Current Mode adjusts the charger’s current when charging a
1.25Ah pack at 1.0C. Initially, the charge current is higher than 1.0C. Within a few minutes
the charger adjusts the current downward, and it eventually reaches 1.0C (1.25A in this case).
Current drops as the pack reaches full charge. When charge current drops to about 0.1C, the
pack is fully charged.
Since Auto Current Mode always starts at the last current calculated during the previous
charge cycle, the charger detects and adjusts for an overcurrent condition: if any cell’s volt-
age increases more than 10% during the first two minutes of charging, Auto Current Mode
defaults to 0.5A. This prevents overcurrent if the previously charged pack had a substantially
larger capacity.
With the 1.0C Auto Current Mode, a fully discharged pack is charged to its nominal capacity
in about one hour. Auto Current Mode takes into account a pack’s starting charge level, so
topping off a 50% discharged pack takes only about one-half hour.
